1. Field
The present disclosure relates to self-humidifying Proton Exchange Membrane Fuel Cell (PEMFC) and in particular, to the design, preparation and properties of a graphene-based proton-conducting composite membrane confined in a porous substrate such as a zeolite, zeotype and/or molecular sieve-coated porous substrate.
2. Background
Perfluorosulphonic acid (PFSA) polymers such as Nafion® from DuPont® are the most common polymer electrolyte membranes used in a Proton Exchange Membrane Fuel Cell (PEMFC) due to their high proton conductivity and excellent long-term stability under a fully hydrated condition. (Nafion is a registered trademark of E.I. duPont de Nemours.) PFSA polymers lose mechanical and dimensional stabilities at high temperature due to its low glass transition temperature, which restricts the operating temperature of PEMFC utilizing PFSA to below 80° C. The low operating temperature brings many problems including greater sensitivity to fuel impurities (e.g., CO, H2S) and complicated heat and water management problems. The proton conductivity of PFSA polymers also suffers a sharp drop under low membrane hydration, resulting in poor performance. Therefore, external humidification equipment is often necessary when using PFSA polymers, which complicates the system design and operation, and lowers the overall energy efficiency. Many attempts have been made to achieve operation without humidification, including redesign of the membrane structure, proton conductors designed to operate under low humidity and high temperature, and self-humidifying electrolyte membranes.